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V alidation and TestEm series

This article provides a general overview and tutorial for the Validation and TestEm series by Michel Maire. It covers applications, comments on the proton and electron range, stopping power in gas, and simulation of the Fano cavity. The article also explains what validation means and how to compare results with established data, experiments, evaluations, and other simulations.

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V alidation and TestEm series

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  1. Validation and TestEm series Michel Maire for the Standard EM group LAPP (Annecy) July 2006

  2. general overview of the TestEm series : like a tutorial • applications • comments on the proton range • comments on the electron range • comment on the stopping power in gas • simulation of the Fano cavity

  3. What does Validation mean ? • Comparison with well etablished data • from experiments • from evaluations • from other simulations The data must be simple enough to be considered almost as single test unit • Check internal coherence • verify that results of simulation are consistent with input data : cross_sections, stopping_power, … • Book keeping • Keep track of the evolution of the physics versus Geant4 version

  4. Two remarks of pratical importance • The results of simulation must be simple enough to be analysed (understood …) easily and quickly • Not more than a few number of 1D histograms • The results and the protocol to get them must be made public, in close connection with the source code distribution

  5. User’s applications : what to inspect ? • Geometry • Physics list • What is recorded and how : tracking, stepping and stacking actions • very often the systematic use of hit/digit structures is not necessary; it may complicate the code for nothing • TestEm series want to be a tutorial and a reference of what to do in this area • extended/medical/gammaTherapy and extended/optical/LXe have similar goal

  6. TestEm series

  7. General principles • The examples try to be generic enough, to allow to handle similar situations without code modifications  always simple (trivial …) geometry • Specific cases are defined via UI macros • The source code is exposed to users. It wants to be a reference for how to compute and plot various physics quantities

  8. Photon interactions Unpolarized, no fluorescence

  9. Charged particle interactions Unpolarized, no fluorescence With cuts

  10. Multiple Coulomb scattering • As an isolated mechanism • mean free path • step limitation • true path length • angular distributions • lateral displacement • correlation • As a result of particle transport • various distributions in transmission absoption reflexion Em15 Em5

  11. More global verifications

  12. Other specialized programs

  13. Histograms management • Creating histograms is always optional, under the control of G4ANALYSIS_USE  need at least one AIDA implementation • A set of 1D histograms is predefined in an HistoManager class  only 1D histograms; no ntuples, no hits structures. • Booking, Filling • a given histogram is selected and booked via UI command • his binning is defined via UI command • Output • the name of the file and its format are defined via UI command  xml, root, hbook

  14. TestEm0 : Input data (via G4EmCalculator)

  15. TestEm13 - 14 : cross sections and final state Direct evaluation of the mean free path

  16. TestEm5 : low energy electron

  17. TestEm5 : high energy muon

  18. Energy deposited along step • the physics computes a step length and a continuous energy loss along step, DE • traditionally DE is treated as a spot at end of step • the step length must be coherent with the desired precision to record or plot DE information by geometry : artificial volumes (voxels, tallies …) by step limiter : step size < histogram binning • more natural solution : spread DE along step point = prePoint+G4UniformRand()(postPoint–prePoint); FillHisto (DE,point);  user stepping action (for time being)  A variant of this idea can be found in examples/extended/medical/gammaTherapy

  19. TestEm11 - 12 : depth dose distribution bin = 10 um without constraint on step

  20. TestEm7 : Bragg curve and tallies

  21. TestEm16 : synchrotron radiation H. Burkhardt

  22. Interaction with users (1)

  23. Interaction with users (2)

  24. Interaction with users (3)

  25. Concluding comments • The TestEm suite consists of 17 generic examples more than 100 macros covering various situations • A subset of macros is part of the regular G4 system test • Em physics lists : standard, penelope, livermore • Many examples have a Geant3 equivalent • Today, the suite covers almost all our basic needs; but it remains in continuous evolution • Automatic running and book keeping must be developed

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